The Swedish Nuclear Fuel and Waste Management Co (SKB) is responsible for final disposal of spent fuel and radioactive waste. SKB operates SFR, an underground waste repository in crystalline rock. The evolution of groundwater flow within the repository needs to be estimated considering different options for the design of the engineered barriers. The goal is to predict the effects of flow and transport on the stored waste over thousands of years to help in the decision-making process of the engineers. This work studies the effects of the different materials in the tunnels used as barriers for the nuclear waste, as well as the materials used to backfill the tunnels after the operational phase, once all the waste has been deposited.